1. Technical Field
The present disclosure relates to an oil separator that separates refrigerant oil from a refrigerant containing the refrigerant oil and a method for producing the oil separator.
2. Description of the Related Art
In general, refrigerant oil is used to lubricate a compressor for use in an air-conditioning device or the like. This refrigerant oil circulates through a refrigerant circulatory system together with a refrigerant. The refrigerant oil taken in from the intake side of the compressor is supplied to each slide member provided in the compressor and is used for lubrication of each slide member. In addition, the refrigerant oil is also supplied to a working chamber. The refrigerant oil seals a gap in the working chamber, thereby preventing leak of vaporized refrigerant.
In the circulatory system, in a case where the refrigerant ejected from the compressor contains a large amount of refrigerant oil, the refrigerant oil is likely to adhere to an inner wall surface of a heat-transfer tube of a heat exchanger. The refrigerant oil adhering to the inner wall surface of the heat-transfer tube inhibits heat transfer of the heat-transfer tube and thereby deteriorates the heat-transfer efficiency of the heat exchanger. In order to avoid such a situation, an oil separator is provided in the circulatory system. The oil separator separates the refrigerant oil from the refrigerant ejected from the compressor and brings this refrigerant oil back to the intake side of the compressor.
The high-temperature and high-pressure refrigerant containing refrigerant oil ejected from the compressor is introduced into a cylindrical oil separator so that a swirl flow occurs. A centrifugal force produced by this swirl flow causes the refrigerant oil to adhere to an inner wall surface of the oil separator. This refrigerant oil moves to a lower portion of the oil separator due to gravity and forms an oil pool. In this way, the refrigerant oil is separated from the refrigerant.
However, the aforementioned oil separator has a problem that the refrigerant brings up the refrigerant oil in the oil pool together with the refrigerant and carries the refrigerant oil to the ejection path for the refrigerant. In view of the problem, Japanese Unexamined Patent Application Publication No. 2005-180808 proposes an oil separator that is configured so that an inner diameter of a lower portion of the oil separator is larger than that of an upper portion of the oil separator. This reduces the swirl speed of the swirl flow in the lower portion of the oil separator, thereby keeping the refrigerant from bringing up the refrigerant oil together with the refrigerant.
Furthermore, Japanese Unexamined Patent Application Publication No. 2005-180808 mentions that the inner diameter gradually decreases from the upper portion of the oil separator to the central portion of the oil separator, and the inner diameter gradually increases from the central portion of the oil separator to the lower portion of the oil separator. According to Japanese Unexamined Patent Application Publication No. 2005-180808, this increases the swirl speed of the swirl flow in the central portion of the oil separator and rectifies the flow, thereby achieving a good separating property.